Apologies if I missed something.......you married in the UK so this is presumably not her first UK visa application..
Did she previously apply for a fiancee visa?
I have also always bought flights before applying - but have never submitted the details with the application as an Entry Clearance Officer (ECO) will simply disregard them as pointed out by @oldgit
If your wife has sufficient funds to cover all costs of a 2 week holiday you can say that you are staying in various hotels and family members. If you are staying with parents you may be wise to get a letter of invitation. Previous applicants have supplied details of the house to show there is adequate accommodation.
@sandyf mentioned you writing a letter outlining details of the relationship and reasons or your visit etc. and that is good advice. However, let's be clear - this is your wife's application and (apart from being her husband) you have nothing t do with it; you don't even need to be 'sponsor' if she is evidencing sufficient funds in the bank.
Without having all the information, it seems that you making this brief visit for family reasons ie it is probably not a holiday at this short notice and only 2week duration. There are 3 key areas than ECO needs to satisfy themselves on:-
Genuineness of Relationship and genuine reason to visit.
Financial adequacy.... She/you must evidence adequate money for the duration of stay. Unfortunately, unlike Schengen visas, UKVI do not give any guidance on this (Spain suggests a minimum of EUR 100/120 per day.).
Reasons to Return to Thailand. The big one. The risk of flight for (younger) Thais is deemed to high by many countries - Australia are particularly hard on this but you seem to have enough in your story (and a marriage certificate) to counter this. Copies of chanotes, or any other document must be translated into English and certified.
Your financial story is interesting and probably incomplete. You have no income but a bit of capital; you have no pension which suggests that you are younger and possibly returning at some point to work. If you are going to make reference to your financial situation in your introduction letter make sure it stands up to scrutiny -otherwise leave it out (and any other reference to you) and just provide the letter, relying on your wife's financial evidence.
In simplistic terms you re a married couple who are building a house in Thailand (which will become your permanent home) and you are making a brief UK visit to see family. After the 2 weeks you will return to Thailand to continue building your house. You can evidence enough money to cover the visit and you have the backup of parental accommodation.