"Canada condemns the decision today by the Royal Thai Army to seize control from Thailand's elected government, to suspend the Thai constitution and to restrict civil liberties," he said in a statement.
"This decision violates Thailand's democratic principles and stands in stark contrast to the army's earlier assurances that its role would be limited to securing public order."
The army under Gen. Prayuth Chan-ocha seized power and suspended the Thai constitution on Thursday.
The army first declared martial law on Tuesday, saying it needed to restore order after six months of political deadlock and increasingly violent protests
The Thai ambassador in Ottawa was called in to hear Canada's concerns directly.
Baird says Canada wants action.
"We hope and expect the Thai military will return Thailand to civilian rule as soon as possible, respect democratic processes and the rule of law, ensure freedom of expression and assembly, and guarantee due process for those who have been detained."
Canadians travelling in Thailand are encouraged to register with Canadian authorities in order to get updates from the embassy, he added.
Earlier in the week, the department urged Canadians in Thailand to exercise a high degree of caution.
"There is a risk of civil unrest, sporadic violence, and attacks throughout the country," the website said.
It specifically warned against travel to the Thai-Cambodian border area in Surin and Sisaket provinces and to the far southern provinces of Narathiwat, Pattani, Yala and Songkhla, including the city of Hat Yai.