Travel advice needed for Nong Khai

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As for the clothing, unless you dont enter a Temple with shorts and cleavage, its fine. 

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I have lived in NK for 7 years,Thailand for 13.My recommendation is that you come with very little clothing.Shorts and blouses are fine for casual wear as tourists.When you get here,you can buy ,very cheaply,lightweight clothing,more appropriate for ''special''occasions!Don't bring any fancy dress up formal type wear at all.Don't get a suntan either.Sandals are the best footwear,as you will be constantly sliding off your foot wearEverything is very laid back here,be prepared for a lot of sitting and kneeling on the floor!

You will probably be expected to contribute to the party,either with money or beer/whiskey,so no family gifts are necessary,except money in an envelope or tied around the couple's wrists!
When you get here,you can buy cookies/candy for the children,if you like.
The more you buy the family,the more you will be expected or asked of you.
The only impression that you want to make is polite,respectful and smiling.Bad impressions are made by not respecting culture,spending to easily or flashy (will set you up for more demands and expectations,then and in the future)or acting in a confrontational manner(face is most important here,do not criticise anything or anyone)!
Don't worry and don't be a sucker!