BANGKOK (Reuters) - Retired diplomat Maris Sangiampongsa is the top candidate to become Thailand's new foreign minister, multiple sources said on Monday, after the previous holder of the post unexpectedly quit having lost his other position of deputy prime minister. 

Maris is a former Thai ambassador to Australia and Canada and was an advisor to predecessor Parnpree Bahiddha-Nukara, whom the government on Sunday confirmed had resigned. 

The sources each had knowledge of the matter but declined to be identified because they were not authorised to discuss it. Maris was approached by the government for the foreign minister portfolio on Monday, the sources said. Maris did not immediately respond to a request for comment. 

Prime Minister Srettha Thavisin earlier on Monday said he had selected a new foreign minister candidate who has "long involvement in diplomatic circles," and who has worked behind the scene at the ruling Pheu Thai party.

Srettha did not disclose the name of the candidate, saying the vetting process was still ongoing.

(Reporting by Panu Wongcha-un and Panarat Thepgumpanat; Editing by Martin Petty)