Four pre-coup political parties saw their memberships plummet by as much as 97% after the confirmation deadline passed on Monday.
They are required by the junta's order to have existing members confirm their status and pay membership fees of 100 baht a year or 2,000 baht for life.
Failure to do so by the deadline means existing memberships are automatically terminated.
Despite the low turnouts, parties are pinning hopes on the lift of the political ban, when they can recruit new members.
Democrat, the oldest party with the largest membership base, reported 3.2% or 80,000 of its 2.5 million members had confirmed. (see chart below)
Deputy chief Ong-art Klampaibul said on Monday the low turnout came as no surprise but insisted it would not affect the party's performance in the upcoming general election.
He cited reasons for the lukewarm interest.
"First, it's not practical to confirm memberships with the junta's ban on party activity in place. Cost is also a concern as people have never been required to pay a membership fee and many think they can help the party in other ways.
"A number of members say they simply don't accept the junta's order No. 53/2560 which they view infringes on their rights. Others confirm membership but do not pay the fees as they can continue to be members for four years as allowed," he said.
He was referring the junta's order widely viewed as an attempt to "reset" old parties and level the playing field for new players.
However, Mr Ong-art is convinced when parties are allowed to recruit new members, the situation will be much better.
Pheu Thai, the ruling party after the last successful election in 2011, estimated 10,000 or 7% of its existing members had confirmed memberships.
"Some 6,000 confirmed as of April 26 and more [requests] are being processed," said acting party leader Pol Lt Gen Viroj Pao-in.
Like the Democrat party, Pheu Thai believes the fees are the major deterrent and that the numbers would be better after the political ban is lifted and the party can recruit new members.
Chart Pattana, which won seven seats in the 2011 election, reported 5,583 or 31% of its 18,163 members confirmed this month, which it deems satisfactory.
"Most of the members who confirmed their status are in Nakhon Ratchasima," said party leader Wannarat Channukul.
Chartthaipattana, with 19 seats in the 2011 polls, reported 2,500 or around 10% of its 24,710 members confirmed their status this month, in line with its forecast.
"We still wait for those who confirmed by registered mail," Pisit Pittayathakulcharoen, the party's registrar said.
Party director Nikorn Jamnong said the confirmation rate was unsatisfactory.
"The low confirmation rates will affect the political system since parties are required to hold primary votes. In order to do so, a party needs to have at least 7,000 members," he said.
According to the timeline in the junta's order, after the membership confirmation, parties will have to raise seed funds of at least 1 million baht by Sept 28 (180 days from April 1).
They are also required to have 500 paying members by the same date, 5,000 by April 1, 2019 and 10,000 by April 1, 2022.
