* Bank of Ayudhya posts record quarterly net profit
* Bangkok Bank profit up 1.2 pct, Siam Commercial Bank down 12 pct
* Bank of Ayudhya profit up 3.2 pct
* Thai lenders lifted by recovering economy (Recasts with results from Siam Commercial Bank)
BANGKOK, Oct 19 (Reuters) - Two of Thailand's leading banks reported higher third-quarter profit on Thursday, with Bank of Ayudhya producing record earnings on the back of a jump in net interest income.
The Thai economy has been gaining momentum with rising exports and recovering consumer demand, which has brightened the outlook for the country's banks. The central bank said last month that banks had high capital adequacy ratios and that the increase in bad loans had slowed.
"We expect the continuation of economic momentum, together with an expected seasonal rise in business for both retail and commercial lending," Bank of Ayudhya President and CEO Noriaki Goto said in a statement on Thursday.
The bank's net profit of 6.01 billion baht ($181.41 million) for the three months to Sept. 30, was up 3.2 percent year on year. It booked provisions of 7.8 billion baht to maintain a strong capital base.
The result fell short of an average estimate of 6.1 billion baht from three analysts polled by Reuters but was still a record-high quarterly profit for the bank.
Thailands largest lender, Bangkok Bank later reported a 1.2 percent rise in third-quarter net profit to 8.16 billion baht.
Net interest income grew to 16.8 billion baht, up 4.7 percent, while non-interest income rose by 7 percent to 11.7 billion baht. The ratio of non-performing loans (NPLs) to total lending remained stable at 3.8 percent
Second-ranked, Siam Commercial Bank, reported net profits of 10.1 billion baht, down 12.2 percent from last year.
The results fell short of market expectations, which predicted earnings of 11.95 billion baht, based on four analysts polled by Thomson Reuters.
Siam Commercial Banks growth was held back from a 13.8 uptick in operating costs and a 4.6 percent decline from last year in fee and commission income, but net interest income grew 4.8 percent.
Higher costs were "in line" with its transformation plans and it also set higher provisions of 7.8 billion baht in preperation for IFRS 9 in 2019, it said in a statement.
Bank of Ayudhyas profit growth was also driven by a jump in net interest income, which rose to 17.3 billion baht from 15.8 billion baht a year ago. Fee and service income rose by about 9.5 percent to 5 billion baht.
Its NPL ratio was stable at 2.16 percent, the lowest level since December.
Bank of Ayudhya, controlled by Japan's Mitsubishi UFJ Financial Group Inc, reiterated that it was aiming for loan growth of 6-8 percent for 2017, with CEO Goto saying the increase would come in at the lower end of the range. (Reporting by Chayut Setboonsarng; Editing by David Goodman and Jane Merriman)