BANGKOK (AFP) -- A Thai general was found guilty of human trafficking on Wednesday as a Bangkok court convicted scores of people in a mass trial exposing the lynchpin role of corrupt officials in the grim, lucrative trade in Rohingya and Bangladeshi migrants.

Thailand's junta launched a crackdown in May 2015 on a network funnelling desperate migrants through southern Thailand and onto Malaysia, holding some for ransom in jungle camps.

It unspooled a crisis across Southeast Asia as gangmasters abandoned their human cargo in the camps where hundreds died from starvation and malaria, and at sea in overcrowded boats which were then "ping ponged" between Thai, Malaysian and Indonesian waters.

After a day delivering verdicts for many of the 102 defendants, Bangkok Criminal Court found Lieutenant-General Manas Kongpan guilty of multiple human trafficking charges.

A judge said he was also guilty of complicity in a "transnational organised crime" network and "worked with others to facilitate human trafficking".

The ruling is an extremely rare conviction for a senior army officer in junta-ruled Thailand.

Manas, the highest-ranking official on trial, was a top figure in the security apparatus covering Thailand's south -- a key transit zone in a trafficking trail that stretched from Myanmar to Malaysia.

The court heard he received bank transfers from trafficking agents worth
14.8 million baht ($440,000). 

But the police investigation found he also used his position to guide trafficking gangs around checkpoints after their arrival on remote beaches as they headed to the jungle camps.

In 2013 he was promoted to head the Internal Security Command (ISOC) for the entire south. Current junta leader Prayut Chan-O-Cha was army chief at the time.

Before the crackdown rights groups had long accused officials of ignoring
-- and even conducting -- the trade in humans through Thailand's southern provinces.

The trial has revealed a lattice of military, police, local political and mafia figures acting as traffickers, agents and logistics men, all soaking up cash from some of Asia's poorest and most vulnerable migrants.

Over the years the smuggling gangs are estimated to have netted tens of millions of dollars.