Upvote:5
I checked the Wikipedia entries for Tehran Airport and Phuket Airport, but I think the direct flight from IKA-> HKT on Mahan Air has been terminated.
That works in your favor, in my opinion, as Qatar Airways seems most friendly to divers. You can fly from Tehran to Phuket via Doha.
From the Qatar Airways website:
Qatar Airlines:
Qatar Airways allows extra baggage allowance only for the below listed sporting equipments... Regardless of class of travel, an additional complimentary 10Kgs will be allowed...
Scuba Diving Equipment: Which consists of suit, vest, socks, mask, shoes, torch, webs, knife, oxygen cylinder and a regulator. Diving cylinders must be empty.