The flag carrier's board approved the postponement on Monday and it will operate four flights per week to Rome with Boeing 747-400 aircraft, it said in a statement on Tuesday.
The airline said the route suspension would be temporary once it did take effect and it may resume operations once the company makes progress on a restructuring.
The postponement came few weeks after it decided to suspend loss-making flights to Los Angeles and to Rome from late October and cut 1,401 jobs through voluntary retirement this year as the airline pushes ahead with restructuring.
Thai Airways is among several state-controlled companies that the military government has targeted for reform since seizing power in May 2014.
Its two-year restructuring plan involves reducing operating costs and capacity by 20 percent, selling aircraft and cutting jobs.