I’ve flown Singapore Airlines twice, on their A380 and the 777-300ER in their okay-comfortable economy.
Singapore Airlines is now offering lounge access for transit economy passengers through Singapore, but in a slightly twisted way.
The Ambassador Transit Lounge Singapore Changi Terminal 3 (if arriving in T2 the T2 lounge is eligible too) has an entry fee of ~SGD$40. Singapore airlines is now offering transit passengers SGD$40 coupons, so you have free access to these lounges. All you have to do is collect coupons near the GST coupon collection and refund.
This, for free? Don’t mind if I do
Of course, the lounge pales in comparison to SQ’s new economy.