This sentence has 3 problems:Laughter is the best medicine to improve our well-being, which is regarded as one of the most valuable welfares.
Thanks, liliput, for the correction.I agree that welfare has a wider sense than well-being and that well-being is the term to use with regards to health.
This sentence has 3 problems:
1) Medicine almost by definition improves our well-being.
2) Welfare would not be used as a plural in this way. Perhaps you could say that well-being is the most important aspect of welfare.
3) I agree with Ecossaise that it would be best to replace the whole sentence with "Laughter is the best medicine". This is such a common expression that to use a different sentence with the same meaning sounds odd.