'Chance' is more about 'luck' - "I have a chance to win a prize", it means something that is possible, but not certain. Like "there is a chance I might miss my train".
'Opportunity' can be more certain, like "tomorrow I will have the opportunity to meet Orlando Bloom" or "an opportunity to meet...". Or you could say "There are more opportunities to find work in Bangkok" or even just "There are more opportunities in Bangkok".
But, you can use either most of the time, for example "I will have an opportunity to win a prize" or "tomorrow I will have a chance to meet Orlando Bloom". These are acceptable, the other ways are more natural maybe, but both are easy to understand.