No no and NO.
While yes, the authenticity of the Thai food served is authentic and tasty. The price for the portions served along with the service are not.
Overpriced with small portions and a server stealing your change is NO GO for me.
Simply put, I've been to authentic Thai places that serve more food and at half the price. I'll admit it might not be AS good as Lotus of Siam, but for those that aren't foodies or even tasted authentic Thai food, you won't ACTUALLY notice the difference except for the hype.
18% gratuity is automatically added for large parties.
Though I don't necessarily agree with this, if the service is at least decent I won't complain.
However, if they don't return the change (even if it were only $3) after an automatically added tip, this is absurd.
As a bonus, after our waiter took the check, he ignored my table for 10-15 minutes until I gave up and left. I was with a big party and needed to leave.
STAY AWAY. There are so many better places to spend your money at in Vegas and THIS IS NOT IT.