The House voted 235-198 in favour of Abhisit. The other PM can?didate was Police General Pracha Promnok, from the Pheu Thai Party - the incarnation of the now-defunct People Power Party (PPP).
Boonchong, spokesman for the 23-member Friends of Newin group - a core faction of the previous Somchai Wongsawat govern?ment - insisted that he was not betraying his former party by voting for a Democrat.
"Please don't call us traitors because we decided to break away [from the former ruling party]. We did it for the country's sake. Everyone is aware of the unprecedented political and economic crises that have gripped the nation.
"There was the airport siege, which badly damaged our tourism industry. Local and foreign investor confidence is at its lowest ebb. The economy is in the doldrums.
"Then, the PPP was disbanded on December 2. That came to a dead end. According to the Constitution Court's ruling, the PPP was dead and we had 60 days to join a new party.
"Obviously, we could not vote for a Democrat-led coalition while we were still PPP-affiliated MPs. But once the PPP was dissolved, we had the choice to vote as we saw fit," Boonchong said.
The current term is his third in the Northeast province.
In his opinion, it's no longer politically viable for Pheu Thai to nominate another candidate to govern the nation.
Having won by a majority in the last general elections, the PPP has already had two prime ministers - Samak Sundaravej and then Somchai Wongsawat - both of whom were thrown out of office by Constitution Court rulings.
This warranted a drastic change in Parliament so the opposition Democrat Party, which won the second-highest number of votes in the last election, could form a new administration.
However, such a change of heart by Boonchong and other MPs belonging to the Newin faction angered supporters of former pre?mier Thaksin Shinawatra in the Northeast.
"After switching camps, I and other defecting MPs have been fac?ing a hard time, including two threats to bomb my house in Nakhon Ratchasima.
"But, I remain undaunted and will explain the situation to my constituents. People from the business sector and the middle class have supported our move.
"Next, we'll have to convince the grass-roots voters of the necessi?ty to change or else they will also be hurt because no tourists will come to Thailand. Then they, their relatives and children could lose their jobs if more factories are shut down because of the political and economic crises.
"In other words, we're stuck in the same boat and we need to move forward," he explained.
As to the Pheu Thai Party, he said: "Not many of my constituents are aware of this new party or its leader. Yet, we would ensure that a number of key populist policies, such as the village fund or SML budget programmes, are included in the new government's agenda."
With regards to the new premier, Boonchong said: "He would have to work very hard to bring all Thai people together to end the national divide caused by pro- and anti-Thaksin groups.
"Economically, he needs to quickly tackle the unemployment and falling farm-price issues, and so on.
"After all, time isn't on his side so the first three months will be a major test of the new PM's mettle."