AirHint found the following cheapest return flights from Chiang Mai (CNX) to Colombo (CMB) in September 2025 (see full year).

Return flights

23 Sep - 13 Oct	Thai AirAsia
23 Sep - 30 Sep	Thai AirAsia
25 Sep - 13 Oct	Thai AirAsia
25 Sep - 30 Sep	Thai AirAsia
23 Sep - 29 Sep	Thai AirAsia
30 Sep - 13 Oct	Thai AirAsia
25 Sep - 29 Sep	Thai AirAsia
26 Sep - 13 Oct	Thai AirAsia
26 Sep - 30 Sep	Thai AirAsia
25 Sep - 15 Oct	Thai AirAsia
30 Sep - 15 Oct	Thai AirAsia
26 Sep - 29 Sep	Thai AirAsia
23 Sep - 06 Oct	Thai AirAsia
25 Sep - 06 Oct	Thai AirAsia
26 Sep - 15 Oct	Thai AirAsia
30 Sep - 06 Oct	Thai AirAsia

Also check the deals for one-way flights from Chiang Mai to Colombo in September.

The deals are updated regularly. The prices may go up as tickets are purchased by other travellers. Only the cheapest flights are offered. Select a price to book and secure these cheap prices.

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Cheapest return flights from Chiang Mai to Colombo in September from $396

Return flights