Many embassies showed reluctance on Sunday to attend the government's invitation to observe security arrangements to control the mass rally heading for Government House on Monday.
So far only Cambodia and Malaysia have indicated they will send diplomats to observe the security operation, according to sources at the two embassies.
The Centre for the Administration of Peace and Order said it had invited diplomats to see with their own eyes its handling of the demonstrators led by the People's Democratic Reform Committee when they set off on Monday morning on their "final rally" march to Government House.
An official at the Singapore embassy said "we have yet to receive an invitation to observe the operations" and hinted that the embassy would not send anyone.
Myanmar embassy sources affirmed that the embassy would not take up the offer, while the Chinese embassy remained undecided. "We have yet to decide which person would be attending," a source at the Chinese embassy said.
A diplomat from Cambodia, however, said an envoy would join the government programme. Thailand and Cambodia have warm relations after the Pheu Thai Party won the last election and Yingluck Shinawatra became the prime minister.
Indonesia remained undecided and Malaysia will send a deputy chief of mission to Monday's protest, sources said.
Other sources said Deputy Prime Minister and Foreign Minister Surapong Tovichakchaikul had asked diplomats to attend a briefing on Monday morning at the Foreign Ministry before proceeding to Government House, the target of the protesters.