The monks will come from 500 temples in Bangkok and several other provinces. They will be joined by Buddhist lay people from across the country. The rally is expected to last until Wednesday.

Phra Thep Wittayakoon, or the well-known Luangpor Koon, of Wat Ban Rai, has donated 10,000 baht to support the movement. It also is endorsed by the World Buddhism Relations Organisation and the Buddhist Association of Thailand.

Luangpor Koon said on Sunday that supporters of the movement had wanted an existing, traditional clause in the draft charter which states that the King must be a Buddhist and and upholder of all religions to include an addition making Buddhism the national religion.

But the nation never has declared a state religion, although about 90 per cent of Thais consider themselves as Buddhists.

He hoped that the Constitution Drafting Assembly would heed the Buddhists' wish when they convene this coming week to debate the draft charter.

The well-known monk also warned that the draft charter might be voted down in a national referendum if it did not contain the clause as wished, he claimed, by most Buddhists.