To me, there's no best lakorn of all time. Almost all of them are lacking something. Even my favorite lakorns.
Here are my favorite lakorns of all time:
Ning and Parson -Ka Neung Ha
Saranyu & Numpung - Mon Ruk Look Toong 1995
Pol & Joy - Samee
Ann & Willy - Manee Yard Fah
Willy & Mew - the one that takes place in the desert
Mew & Saranyu - Wanida
Pip & Bongkot - Nirad Song Pope
Til & Aom - Roy Lie snah rai