The official data marked a 99.8% fall compared to December 2019, when 3.95 million arrivals were recorded.
Thailand has for four months welcomed long-stay visitors who agree to undergo two weeks of quarantine, following a lengthy ban on tourists and commercial flights that was imposed in April and devastated its economy.
Authorities are offering domestic travel incentives to spur Thai tourism but those efforts have been hit by a fresh coronavirus outbreak that has seen infections more than triple in just over a month, although its cases are still less than 14,000 in total.
In 2020, the foreign arrivals plunged 83% from a year earlier to 6.7 million - of that 6.69 million were in the first quarter before the ban was imposed in April.
Their spending amounted to 332 billion baht ($11 billion) compared to the 1.91 trillion baht ($63.75 billion) spent by nearly 40 million tourists in 2019, which was worth 11.3% of gross domestic product.
The state planning agency has forecast only 5 million foreign visitors for 2021. However, Finance Minister Arkhom Termpittayapaisith told Reuters last week that projection was still uncertain.
On Monday, Thailand said it would start its coronavirus inoculation programme next month.
($1 = 29.96 baht)
(Reporting by Orathai Sriring; Editing by Martin Petty)
