Presumably you booked one of these fare types, all of which include 20kgs. Your 10kgs (900 baht per person per flight I think) is in addition to the standard 20kgs so you'll be fine with 30kg.
Not on Bangkok Airways by the looks of it, unless there is another cheaper fare class with no baggage allowance. Saving time would only happen if you have poor time management and waste the time waiting for your bags instead of doing something productive.