Anti-graft officials say they will investigate why the wife of former prime minister Chavalit Yongchaiyudh has paid no tax - despite having seven times the declared net worth of her husband, who did pay tax.
Thais have traditionally shunned the tax man and officials have rarely had the nerve to probe powerful members of the establishment.
But a new corruption commission will soon be given powers to dig up the dirt on politicians and members of the bureaucracy.
Phankrua Yongchaiyudh's lopsided share of the claimed family wealth was revealed this week as part of the former Cabinet's assets declaration.
Thai governments have to publicly list their wealth before and after taking office to try to combat political corruption.
'In the past the public expected MPs to be dishonest - it was inevitable like rain in the rainy season,' said a member of the commission.
'But attitudes have changed - the public are angry that bad politicians allowed the economy to collapse.