They say the sunset at Promthep Cape is spectacular. I hav e never made it, as the sunset can be seen in many places. The veiws at the Cape however are great. Well worth the drive (it isn’t far).
I will let you into a little secret. Just South of the cape, driving on the main road, there is a side road, 200m on the right hand side. Follow that for 300m and you come into some temple grounds. Behind the furthest building is some steps to a veiwing platform. Make the effort to visit here, its well worth the rewards.