BANGKOK, Aug 13 (Reuters) - Thailand's cabinet on Tuesday agreed to increase the size of an existing government equity mutual fund to invest in Thai stocks, a deputy finance minister said, as the government seeks to support Asia's worst performing bourse this year.

The fund will be positive for the capital market and provide an option for savings, Paopoom Rojanasakul told reporters, without disclosing the increased fund amount.

Finance Minister Pichai Chunhavajira has previously said the size of the Vayupak Mutual Fund would be raised by 100 billion baht ($2.84 billion) to 150 billion baht.

Pichai and other officials will hold a press conference on the fund later on Tuesday.

The Vayupak fund's current top holdings include Thailand's largest oil and gas firm, PTT, financial group SCBX and Krung Thai Bank, fund data showed.

Thailand's main stock index has fallen 8.4% so far this year to be the worst performing market in Asia, with foreign investors selling 120 billion baht ($3.4 billion) worth of shares during the period.

The Thai market slumped 15% last year.

($1 = 35.15 baht) (Reporting by Kitiphong Thaichareon and Thanadech Staproncharnchai; Writing by Orathai Sriring; Editing by John Mair)