Besides 'LOL', there are many options to express laughter after reading a funny text message. Here are five alternatives for 'LOL':
Haha or HAHAHA in capitals for true laughter
LMAO (Laughing My Ass Off)
ROFL (Rolling On the Floor Laughing)
I can't stop laughing
I'm cracking up
You can choose one of these expressions to express that you find something funny. Especially knowing that 'LOL' or 'Haha' can be weakened through repeated use. Keep in mind that the above suggestions have no place in professional communication, like emails or even text messages. Use a complete phrase instead, for example: 'That's so funny'.