Answer
Start by comparing the option against the practical details that will affect the experience, not just the headline price or a few attractive photographs. For learning Thai cooking, confirm written recipes, ingredient substitutions, technique notes, spice adjustment, videos or follow-up material, sourcing ingredients at home, allergies and permission to photograph.
The most useful class teaches principles-balancing salty, sweet, sour and spicy-rather than only a fixed recipe. Ask how local ingredients can be substituted without losing the dish's character.
Ask for the important points in writing before paying or making a firm plan, especially anything involving availability, safety, deposits, inclusions or cancellation. Current operating details can change with the season, weather and staffing.
A reliable provider or organiser should be willing to explain what is included, what is not included and who will take responsibility if plans change.