Army leaders may be questioning the power of their political influence after the sweeping defeat of the Democrat Party extended even to the military vote.

The Royal Thai Army is known as a staunch Democrat ally, but the results of Sunday's election reflected that while its top brass can mould their subordinates on the battlefield, it failed to shape their political ideologies.

Army chief Prayuth Chan-ocha is a vocal Democrat supporter and while he stopped short of outright ordering his soldiers to vote for his party of choice, he made his preference clearly known.

Despite this, army votes for Pheu Thai point to the high number of "watermelons" in the military. This nickname refers to their uniform marking them as green on the outside, but their personal beliefs making them "red" within.

Some of these "watermelons" have close ties with Pheu Thai and/or the red shirt movement, while others are just sympathetic to the party or the cause.

Army leaders must have been especially incensed when Pheu Thai's Leelawadee Watcharobol won a seat in Dusit district, which has a high military presence with many army units.

With Pheu Thai now in the process of forming its government, the Democrat Party has been consigned to the opposition bench. Gen Prayuth will surely be disappointed with the result and will likely be brooding over "what went wrong".

Even before the election was announced, Gen Prayuth's hostility to the red shirts and opposition to Pheu Thai was clear, and all army personnel were well aware of their boss's thoughts on political matters.

An army source said that although soldiers were not told to vote a certain way, they all knew Gen Prayuth favoured the Democrats and was hoping they would follow his example.

The source said that while it was too risky for unit commanders to order the rank and file soldiers to vote a certain way, commanders still attempted to exert influence.

For example, videos of the burning of parts of the city at the culmination of last year's red shirt protests were played in barracks on most days in the run up to the election, the source said.

But the vote results suggest the efforts were in vain, and point to the real feelings of many soldiers who until now had held their political tongue.

And even if some soldiers did go along with their commanders' bidding, it would not have been enough to offset the pro-red votes of their families, as many troops come from areas which traditionally favour Pheu Thai.

There was also likely an element of personal interest for some who voted for Pheu Thai, as many soldiers once worked for army leaders who have close ties with former prime minister Thaksin Shinawatra.

Many of these superiors had been transferred to inactive posts in the post-Thaksin military landscape, but a new Thaksin-influenced government could see them return to positions of power, and with that would come increased prospects of promotion for their former subordinates.

A private from a military unit on Nakhon Chaisi Road in Dusit district said after casting his vote on Sunday that his commander did not order him to vote for the Democrats but he knew this was what his superior wanted.

"I had two ballot papers. On one paper, I voted just as my boss wished. On the other one, I made my own choice," said the soldier, who did not wish to be named.

With the army long suspected of political involvement, it is a healthy sign for democracy that many soldiers voted in a different direction to that of their bosses' stated preference.