Partial search match on synonym

OpenSearch
1

I am trying to setup opensearch index for searching projects inside our database. The mapping looks like this

{
  "properties": {
    "name": {
      "type": "search_as_you_type"
    },
    "countries": {
      "type": "text"
    }
  }
}

My example data looks like this, consists of project name and countries that the project resides. In this example the project’s in Thailand and Laos.

{
  "name": "DXPC comare",
  "countries": ["TH", "LA"]
}

I have a synonym set up to convert the search text to synonym. These are the configuration in the analysis block.

{
  "analyzer": {
    "country_analyzer": {
      "tokenizer": "standard",
      "filter": [
        "lowercase",
        "country_analyzer_filter"
      ]
    },
  },
  "filter": {
    "country_analyzer_filter": {
      "type": "synonym",
      "synonyms": [
        "australia => AU",
        "austria => AS",
        "thailand => TH",
        "lao => LA",
        "madagascar => MG",
        "united states of america, usa => US"
      ]
    }
  }
}

Now I can make the search works for the name thanks to the search_as_you_type type. But I wanted to make the countries tab behaves the same, meaning I wanted to make the search return the DPXC comare project when I search for tha, thai, and thailand. At the current time, the said project would only return when I search for thailand only. How can I configure my server or change how I sync the data from postgres to achieve that? Thank you for the responses and please comment if you need more explanations.

I am running AWS Opensearch Serverless.