Customers buying into the Bt30-billion bond offering will be paid a return at progressive rates that depend on how long they hold the investments but the average return will likely be 5.1 per cent a year.

Those who hold the bonds up to six month will get 4.5 per cent; seven to 12 months 4.75 per cent; 13 to 18 months 5 per cent; 19 to 24 months 5.5 per cent; and 24 to 30 months 5.75 per cent.

GSB said bonds would be denominated at Bt10,000 and customers would be able to buy up to Bt5 million worth.

"We aim to provide an equal opportunity for all our customers to subscribe to the bonds," said a GSB spokesperson.

The bank will pay returns every six months with transfers to savings accounts and the investments can be redeemed after a month but it will not pay any interest before the half-year mark.

The bonds are transferable to financial institutions or other individuals and can be used as collateral for loans.

Earlier this week, large banks raised interest rates for the fifth time since last September. Their three-, six-, and 12-month deposit rates stand at 3-3.75 per cent, 3.25-4 per cent, and 3.5-4.25 per cent, respectively.

Yesterday, Kasikornbank announced it would increase deposit rates today by 25-75 basis points following similar moves by its peers. The bank's three-, six-, and 12-month deposit rates will be raised to 3-4 per cent, 3.25-4 per cent, and 3.75-4.25 per cent, respectively. The bank's 24-month rate will be raised to 4.25 per cent. The bank's minimum lending rate, minimum overdraft rate, and minimum retail rate will be raised to 7.25 per cent, 7.5 per cent, and 7.75 per cent, respectively.

Thanachart Bank yesterday said its savings account rates was raised yesterday by 0.75 per cent to 2.75 per cent, the highest in the banking sector.