BA v Thai v Emitates
 

I'm new to the forum but need some advice! I will be flying London to Bangkok return around 8 times per year due to a new job. Flights will be in economy and and paid for by me so i'll be looking for the cheapest flights.
I'm thinking it makes sense to use one airline only to get points and hopefully upgrades and lounge access. I've flown with BA, Thai and Emirates previously and all are ok and allow golf clubs for free as part of checked baggage allowance. Emirates are indirect which isn't ideal but they do fly from gatwick which is closer to home than heathrow.
I'm looking for advice on which membership program is best and easiest to obtain a decent membership level which will give upgrades and lounge access.

BA seems fav at the mo as i can deduct their avois from the cost of the next flight when booking but they only give 23kg of baggage allowance which isn't great.

Thai give 30kg but you can't deduct miles from the cost of flights unless flying from BKK to London return and not the other way round. Their gold status membership does sound good though.

I don't have any knowledge on Emirates frequent flyer program.

All advice and suggestions greatly appreciated.