Those making deposits included caretaker Interior Minister and party leader Charupong Ruangsuwan, party election director Sompong Amornvivat, party spokesman Prompong Nopparit and party members Bhokin Polakul, Chusak Sirinin, Kanin Boonsuwan and Ruangkrai Leekijwattana.
The money was deposited in the GSB branch at Bangkok Tower on New Petchaburi Road.
Mr Somchai said his party members made the deposits with the intention of increasing the liquidity of the state-owned bank after a large number of people withdrew money from the institution on Monday.
The mass withdrawals came after GSB confirmed a five billion baht loan to Bank for Agriculture and Agricultural Cooperatives (BAAC) on Sunday.
GSB confirmed on Monday that it would suspend further lending to BAAC after 30-billion-baht was withdrawn by customers amid concerns the loan would be used to pay for the caretaker government's rice-pledging scheme.
Mr Somchai said he and his colleagues had deposited money with GSB because they wanted to help farmers suffering as a result of overdue rice payments, caused by the fact the caretaker government had limited authority to spend state money following the dissolution of the House of Representatives.
The former prime minister said he will urge more party members to deposit money in GSB at a meeting of former MPs later today.
Pheu Thai will also launch nationwide campaigns to encourage people to deposit money in GSB, he added.
Mr Somchai said he believed his party’s campaign will ensure that GSB has sufficient funds to provide loans to BAAC, so that it can make overdue rice payments.
He claimed that delays in rice payments were the fault of anti-government groups, including the People’s Democratic Reform Committee (PDRC), adding that he could guarantee on behalf of government that every farmer will get the money owed to them.
Jatuporn Prompan, co-leader of the United front for Democracy against Dictatorship (UDD), meanwhile called on red-shirts and all Thai people who love democracy to help deposit money in GSB, Asia Update satellite television station reported.
Mr Jatuporn said people would be helping make sure that GSB has enough liquidity to offer loans to the BAAC in order to pay rice farmers.