Flying in to BKK regularly via SQ & always wanted to know what was needed to secure a premium lane coupon for arrival at Suvarnabhumi. Showed flight attendant one of the. (usless) SQ express arrival coupons which are given to SQ gold in Brisbane & asked for a BKK one as they were handing them out. Was advised that they were for those PAX who paid for a fully flexible ticket, & business. / first I suppose. Success! I ended up with two of them, undated, no flight number. Didn't need to use this time but will be happy next time the queue is a mile long.