BANGKOK, Thailand -- Security officials sifted through the grizzly
remains of victims and wreckage in the streets on August 18, but said
they did not know who detonated a powerful pipe bomb in the heart of
Bangkok crowded with shoppers, tourists and rush-hour commuters.

The blast killed at least 19 people -- including foreigners -- and
injured 123 others but no one immediately claimed responsibility.

Officials began inspecting CCTV evidence of the explosion which set
off a billowing fire when nearby motorcycles ignited.

They will also be scrutinizing personal videos recorded by screaming
pedestrians who fled in all directions and later posted their escapes
online.

Rescuers removed the corpses they had covered with white sheets where
they lay in the intersection, though some said they could retrieve
only body parts around the Hindu shrine and sidewalk.

The military's powerful Internal Security Operation Command (ISOC) was
reportedly pursuing three possible motives, including opponents
against the coup-installed military regime, infighting among the
junta's officials who will soon be promoted or demoted during a
reshuffle, or possible international terrorism by Islamists linked to
Iran and the Middle East.

ISOC "ruled out insurgents from the deep South," said a brief report
in The Nation newspaper which did not elaborate.

In the absence of any transparent accountable investigation, Prime
Minister Gen. Prayuth Chan-ocha's harsh restrictions on freedom of
speech are expected to result in rumors and propaganda pushed by all
sides anxious to use the explosion for their own political reasons.

Security forces tried to determine if the location of the blast was
symbolic, while no one immediately claimed responsibility.

Ratchaprasong intersection is equivalent to New York's Times Square.

It became a blood-stained site in March 2010 when the military crushed
the last stronghold of a pro-democracy insurrection resulting in 90
deaths, mostly civilians, during nine weeks of clashes.

Gen. Prayuth seized power in a bloodless coup in May 2014.

He then officially retired as head of the armed forces, but retains
his military title and influence while ruling with absolute power as
prime minister.

The intersection is flanked by some of Bangkok's most expensive
shopping malls, five-star hotels and condominiums, and is underneath a
packed commuters' Skytrain monorail serviced by a popular station.

The elegant Erawan shrine, dedicated to a four-faced statue of the
Hindu god Brahman, was also damaged by the bomb attached to a pole
along its decorative iron fence.

The shrine's casualties included some of the throngs of worshippers
and tourists who squeeze into its open courtyard every day and evening
to pray at the gilded Brahman and watch ornately costumed Thai women
perform ritual dances.

The shrine is surrounded by Thai vendors selling flowers, incense,
temple icons and live sparrows trapped in bamboo cages which are set
free by superstitious customers who expect a reward of good luck for
their good deed.

Thailand's population is majority Buddhist, but the monarchy and
government include Hindu deities among its official symbols and
institutions.

The shrine is popular among Buddhists because Siddhartha Gautama --
the Buddha -- was born as a Hindu 2,558 years ago, and Hinduism's
ancient religion's clergy are influential in Thai society which also
absorbs countless animist beliefs.

The military's ISOC is heavily involved in fighting Islamist
insurgents in southern Thailand, and also provides intelligence and
security for this Southeast Asian nation's other major military and
political problems.

Thailand's politicized, U.S.-trained military has faced difficulty
containing the strategy-savvy Islamist guerrillas in the south along
the border with Malaysia.

Bombs hidden in cars, motorcycles and cooking gas cylinders are
frequently used by the southern rebels, but there has never been any
publicly confirmed attacks here in Bangkok by the insurgents.

Minority ethnic Malay-Thai Muslims, fighting for an independent
Pattani homeland, form a majority in three southern provinces where
fighting on all sides has resulted in more than 4,500 people killed
since an upsurge in 2004.

The explosion was "more likely to be some anti-junta activists,
although the bombing appears to be sophisticated," said
Washington-based Council on Foreign Relations fellow for Southeast
Asia, Josh Kurlantzick.

The "bombing was clearly intended for the highest possible
casualties," Mr. Kurlantzick tweeted.

At least 19 people died including 13 at the site and six more in
hospitals, the official Erawan Emergency Health Center reported.

Thailand's military regime, which has ruled since the 2014 coup, has
been hit with rising criticism even among supporters, mostly because
its bustling economy has flattened since the junta seized power.

The political conflict mentioned by ISOC presumably referred to the
coup-installed regime's difficulty in crushing pro-democracy
supporters angry that their popularly elected prime minister Yingluck
Shinawatra was ousted in the coup and the constitution subsequently
cancelled.

Gen. Prayuth is currently orchestrating a new constitution which his
opponents predict will be a "constitution from hell".

Leaked drafts and proposals suggest the constitution will allow
appointed military regime figures and collaborating technocrats to
continue their domination by severely restricting the number of
elected political seats in the next parliament.

Gen. Prayuth earlier participated in a 2006 coup which toppled Ms.
Yingluck's older and more popular brother, former prime minister
Thaksin Shinawatra, who then fled abroad to avoid a two-year prison
sentence for corruption.

Last week, Mr. Thaksin told his followers to oppose the next
constitution, sparking concerns that fresh confrontations may be
looming.

Hours after the explosion, Mr. Thaksin expressed his condolences on
his official Twitter account, and condemned the assault.

ISOC's speculation that Gen. Prayuth's upcoming reshuffle may be
linked to the explosion may involve his upcoming shuffle of his
hand-picked, lackluster ministers and other administrators.

Some Thai analysts suspect splits may be worsening within the military
and also among the junta's supporters because the regime has not
solved many of this country's woes but has succeeded in promoting Gen.
Prayuth's allies.

In August 2006, after surviving what he described as an assassination
attempt, then-prime minister Thaksin said a car bomb packed with
explosives near his house was a plot by military officers to stage a
coup.

Mr. Thaksin's Defense Minister General Thammarak Isarangkun agreed and
told journalists at the time: "There is a movement to bring the
government to collapse and to kill the government's leader."

One month after Mr. Thaksin expressed his fears, he was ousted in a
non-violent coup.

ISOC's mention of international terrorism reflects previous attacks in
Bangkok by Islamists allegedly linked to Iran and other Shiite groups
in the Middle East.

But those occasional bomb blasts and possible assassination attempts
have usually been described as plots against Israeli diplomats.

For example, in February 2012, three Iranian men were arrested shortly
after setting off a series of clay-like C-4 bombs in Bangkok which
destroyed their rented house, damaged a taxi, blew off the legs of one
of the Iranians, and injured four Thai civilians.

The arrested Iranians allegedly made their bombs by hollowing out
cheap plastic radios, which they stuffed with C-4 explosives, several
magnets, and some steel ball bearings to increase the destruction.

The pin and handle of a grenade was shoved into the side of each
radio, so the attacker could approach a car, magnetically stick the
radio onto the side of the vehicle, and then manually pull a circular
ring to yank out the pin -- similar to a hand grenade.

The Iranians were allegedly building bombs with C-4 explosives in a
Bangkok house when it blew up, apparently by accident, prompting the
trio to flee.

Police said a fourth Iranian man suspected of involvement, plus the
group's alleged Iranian female accomplice, successfully escaped by
flying from Bangkok to Tehran.

Ironically, the entire Ratchaprasong intersection and surrounding area
is one of the most heavily monitored urban crossroads on earth, with
dozens of CCTV cameras mounted at scores of locations, installed after
the bloody end of the 2010 insurrection.

Pedestrians and vehicles approaching and passing through the area can
be observed and recorded from multiple angles, step-by-step non-stop
throughout the intersection and surrounding streets, through live
feeds monitored on screens in a police bunker in a nearby five-star
hotel.

Those CCTV cameras are also linked to internal CCTV cameras inside
surrounding shopping malls, hotels, office and residential buildings
and elevators, which allow police to watch if their target travels
from the street into a nearby building.

Fortunately for the blasts' injured victims, several well-equipped
hospitals and clinics are very close to the site, which police later
cordoned off during their investigation.

Several Thais and foreigners expressed dread that more confrontations
may result.

They also predict Thailand's lucrative tourism industry will
immediately suffer cancellations because many travelers come to
Bangkok for shopping and sightseeing in and around the Ratchaprasong
intersection during their visit.

Louis Vuitton's opulent showroom, the Grand Hyatt Erawan's plush
hotel, and other multinational venues near the site suffered shattered
glass from the explosion.

Bangkok remained tense but calm after the blasts, but officials
announced more than 430 schools in the capital would be closed on
Tuesday, perhaps to ease parents' concerns over the safety of public
and private transport.

"The perpetrators are cruel and heartless because they intended to
take lives," National Police Chief Somyot Poompanmoung announced in a
televised broadcast.

"Everyone knows that at 7 p.m. at the shrine there are a lot of people
gathered around there -- both Thais and foreign tourists -- and if
they plant a bomb there they know, or can assume, they will cause
casualties.

"The blast radius of the bomb is about 100 meters (about 325 feet).
The bomb experts say that the bomb weighed about three kilograms
(about six pounds).

"We haven't ruled out any motive. We are putting great importance on
every motive," Mr. Somyot said.