I work in Thailand and have a Work Permit valid until December 2018 (which will be renewed by my Thai employer then).  Recently I got a One Year Extension of Stay permit and a One Year Multiple Entry Re-Entry Permit, both valid until 31 July, 2019.

 

I plan to be traveling outside of Thailand in July 2019, and would like to renew the Extension of Stay Permit and Re-Entry Permit before I leave.  Are there any restrictions on 'when' I can renew those?  Can it be done as early as 30 - 60 days before the current permits expire (sometime in May or June, 2019)?  Based on the current rules of course, which I know can change by then.

You can apply 30 days before, 45 days at some offices.