Activist Srisuwan Janya will on Monday ask the Auditor-General to investigate executives and officials at the Bangkok Metropolitan Administration (BMA) in connection with two incinerator projects.
The projects are a 5.6-billion-baht waste disposal system at Nong Khaem in western Bangkok and a similar facility, worth 5.7 billion baht, in On Nut in the Sukhumvit area.
City Hall announced the two winning bidders for the incinerators on Aug 30. Each will have the capacity to handle 1,000 tonnes of rubbish a day.
The BMA will reportedly pay the companies about 900 baht per tonne of rubbish they deal with.
"These rates are unusually high," said Mr Srisuwan when comparing them to similar state waste disposal agreements.
Officials in Khon Kaen pay between 250 and 490 baht a tonne while Phuket municipality is charged 300 baht a tonne, the activist said.
Mr Srisuwan, also president of the Stop Global Warming Association, said he does not understand why the city needs to hire the companies at all when there is the option of generating electricity from the waste for a profit which does not seem to have been explored.
He also asked the auditor-general to look into the firms' financial performance too as one of two firms appears to have cash flow issues.
He also alleged some executives appear to work for both companies.
Mr Srisuwan said he suspected the city's push for the projects may violate the Government Procurement and Supplies Management Act.
Lastly, he added, the bidding appeared to have been rushed as City Hall gave people only four days to air their views in a public hearing.
That, Mr Srisuwan said, is far less than the 21-day period granted for a similar incinerator in another part of Bangkok.