Although my initial plan was to go alone, I had a room mate for a portion of my stay at the Rama. She arrived a few days after my surgery, and left for the amount of time required for hers, and to be honest it was very nice having the companion, even in a sense that there's someone in the room with you.
But for the time I was by myself... Well, there were some harder days but looking back it was fine overall. Immediately post-op after getting back to the hotel, I was an emotional wreck so it's probably best nobody was there to see it. There also one bad night I had a really severe fever, hot flashes and all that fun stuff and I wish someone had been there, but oh well, I lived.
As far as handling yourself physically, you won't be able to leave your room for some time anyway, and you'll be in bed most of the time. I was at the Rama, they restock water and soda daily, room service is veeeery cheap, if you get breakfast service, the food given can last you til dinner. Just buy some stuff that won't go bad fast before the surgery and you should be alright on your own, I was eventually able to go to the local 7/11, Tesco a few times ( although it's further down the block and there's a set of stairs ), even down to Seacon Square on my last day in Thailand. Also, the local KFC and Pizza Hut deliver if you have the hotel staff order it for you.
For the travel home, since you'll likely be able to walk by then, you don't need a companion. Use the wheelchair service at the Bangkok airport, so you can just dash through security and be at your gate in no time, as opposed to waiting in lines, on foot. The only line you'll have to wait in is to check in your luggage, then you flash the paper Chett will give you and the wheelchair guy will handle everything for you from then on. And they'll give you a better seat!
If you have a connecting flight, just flash the paper to somebody from the airport staff again after you land, I personally didn't since the airport was smaller and not very crowded so it was a piece of cake.
To sum up, it's not neccessary to have a companion, I was fortunate enough to have it for the time that I had, it makes the time pass quicker, but if you can occupy yourself well enough you should be fine.
