"Why don't they understand our situation? How can they approve a rise of only Bt400 given the rising cost of living?" Chaisit Suksomboon, who heads the bank's labour union, said yesterday.

According to him, despite Bangkok Bank recording net profits of Bt20 billion last year it had repeatedly ignored union requests for a pay increase. When the bank's executives finally approved the request, they increased each employee's monthly salary by just Bt400.

Chaisit said it was especially unfair as many employees had recently taken on greater responsibility following the merger of a number of positions.

"The bank has long tried to make itself look good in the eyes of the public. It offers a nice starting salary of Bt12,900 a month, but increases are rare. Employees who have 10 years' service are paid less than Bt2,000 more," he said.

Chaisit expected about 1,000 employees to wear black and gather at the bank's headquarters each day. "The protest will continue for one year," he said.