Since nobody has responded yet, I thought I'd chip in with these (you may have already seen some of them but here goes anyway).
1) 2 Moons The Series - Thai BL fluff. Complete fan-service show where both main leads have been secretly in love with each other from episode 1 but their different personalities prevent them from hooking up early. Acting is not the best and there are plenty of cheesy drama cliches.
2) 365 Wun Haeng Rak - Thai rom-com lakorn. Both main leads fall in love and even got married by episode 1. The rest of the show takes you through a ride of post-wedding issues, misunderstandings, working through differences in personalities and dealing with terribly interfering third parties galore. Proper soap opera but happy ending.
3) Angel Eyes & 4) The Moon That Embraces The Sun & 5) My Love Eun Dong - K-drama 'falling in love during childhood days' tropes. Not sure if you count these in but they are technically the main leads and it is by the 1st episode.
6) Jai Rao - Thai melo lakorn. Both leads were deeply in love from 1st episode but a sudden separation traumatised the main male lead. Serious melo and angsty scenarios ensues. Another proper soap opera.
7) Karn La Krang Neung Nai Hua Jai - Thai romance/ action/ mafia lakorn. Main leads definitely fall in love by end of 1st episode. Him being a mafia gang leader and her being miss ordinary is a huge basis for conflict and all sorts of crazy drama.
8) Love O2O - Chinese romance drama. I guess debatable whether main leads really fall in love by 1st episode but they certainly were an in-game couple by the end of 1st episode. Well, he proposed online marriage by end of 1st episode and they were married the next. The rest is history.
9) Roy Fun Tawan Duerd - Thai romance/ action/ mafia lakorn. Main leads were already in love by 1st episode but warring mafia politics and enemies create all manner of conflicts and drama.
10) Summer's Desire - Chinese love triangle romance. 2 male leads fight and vie for the affections and love of the female lead from teenage days leading to major casualties and fallout which will impact all 3 into their adult lives. Another real soap opera. The female lead loves both - proper triangle situation.
11) Tatta Hitotsu No Koi - J-dorama romance. Main leads fall in love by 1st episode but rich-girl-poor-boy situation causes loads of difficulties. Sweet and nice romance though!