BANGKOK, July 4 (Reuters) - Thai mobile operator Advanced Info Service Pcl (AIS), plans to invest 32.4 billion baht ($908.84 million) to acquire Triple T Broadband and units held by the JASIF infrastructure fund, AIS said on Monday.

The combined entity would become Thailand's second-largest broadband operator with 35% market share behind True Corporation Pcl, which controls 38%.

The investment will financed by debt, AIS Chief Financial Officer Tee Seeumpornroj said in an analyst call.

"This acquisition will enhance consumer access ... by improving broadband inclusion in new areas targeting the up-country and non-city areas," Tee said in the firm's stock exchange filing.

AIS plans to buy Triple T Broadband for 19.5 billion baht and purchase a 19% stake in JASIF for 12.9 billion baht.

The investment plan comes as Total Access Communication Pcl (DTAC), controlled by Norway's Telenor, seeks to merge with rival operator True, pending regulatory approval.

AIS said the transaction is subject to regulatory approval and is expected to be completed in the first quarter next year.

Thai telecommunication shares were up on Monday, with AIS gaining 1.77% at 0900 GMT, while True was up 0.43%. DTAC and JAISF shares fell 0.56% and 4.74%, respectively.

Those compared with a 0.67% decline in the benchmark index .

($1 = 35.6500 baht) (Reporting by Chayut Setboonsarng Editing by Ed Davies, Martin Petty)