Some good news regarding Single Entry Tourist Visa (SETV). Having looked at a number of Royal Thai Embassy websites from around the world last night I noted that the following message is displayed at the top of their visa information page:
“Temporary Exemption of Tourist Visa Fee (Single Entry) from 1 March 2017 until 31 August 2017.
Only for nationals of Andorra,
Bulgaria, China including Taiwan, Cyprus, Ethiopia, Fiji, India, Kazakhstan, Latvia, Lithuania, Maldives, Malta, Mauritius, Papua New Guinea, Roumania, San Marino, Saudi Arabia, Ukraine and Uzbekistan
applying for Tourist Visa (single entry) to Thailand during the mentioned period will be exempted from the visa fee; ….”
So being able to get a free SETV is another very good reason for getting one before leaving France. ^^
I have looked at the Royal Thai Embassy French website
http://www.thaiembassy.fr/ but have been unable to locate the above message.

That said, what is applied in other countries will also be applicable in France, but it may be worth giving them a call to confirm.
I also note that the information given regarding SETV applications now states:
“
Visas issued must be used within 3 months from the date of application. Upon arrival in Thailand, the actual length of your stay (starting from the date of entry), shall be determined and granted at the discretion of Immigration Officers”.
So if you intend to get a ‘free’ SETV before departure it may be best to apply one month before departure.
Hope this helps.