Many Twitter users have been venting their disappointment with the result of parliament's vote to select the prime minister late on Wednesday night, making the hashtag #RIPTHAILAND Thailand's most popular Twitter trend.

A few hours after it emerged that Prime Minister Gen Prayut Chan-o-cha won the support of 500 parliamentarians to remain as premier, #RIPTHAILAND topped the list of most used hashtags on Twitter in the country, with 457,000 tweets containing the hashtag by about 2am on Thursday.

Thai-language and English-language users also tweeted #lueknayok (#Select a prime minister) and #NotMyPM after the prime minister's selection results were released.

In his response to the tweets, Deputy Prime Minister Gen Prawit Wongsuwon said he thought it was nothing out of the ordinary in politics.

However, he did not want the public to pay too much attention to the parliamentary process of picking a premier, which was a done deal.

Future Forward Party (FFP) leader Thanathorn Juangroongruangkit gained 244 votes in the joint sitting and was defeated as a prime ministerial candidate.

Mr Thanathorn said afterwards that he had been robbed of his victory.

In another development, the Student Union of Thailand (SUT) vowed to fight what it described as an attempt by the military regime to hold on to power.

"The SUT is deeply saddened by parliament's resolution to endorse the selection of Gen Prayut as prime minister," the union said.

The SUT is more than happy to cooperate with any effort to stop Gen Prayut and his cronies from prolonging their stay in power. It is encouraging all parties to join in the fight, according to the group.

The SUT accused Gen Prayut of lacking qualifications to be a prime minister because he led the May 22, 2014 coup that the student body said tore up the constitution and undermined democracy.

The SUT also alleged Gen Prayut turned a blind eye to corruption allegations concerning some of his close aides with the government violating basic rights like freedom of expression of the people, including student activists, with the help of Gen Prayut's special power allowed under Section 44 of the charter.