I want to deploy on server with specify subpath url

[teeraphong]

I follow with this "https://stackoverflow.com/questions/60452054/nextjs-deploy-to-a-specific-url-path"

I config 'next.config.js' with this code

`const nextBuildId = require('next-build-id')

const isProd = process.env.NODE_ENV === 'production'

// Enable importing of css stylesheets
const withCSS = require("@zeit/next-css")
const withImages = require('next-images')

/*

• Gets the BASE_PATH from the command used to start this app.
• If BASE_PATH is specified but it does not start with a "/"
• then add it.
  */
  function getBasePath() {
  const basePath = isProd ? '/purchases/' : ''

console.log('process.env', process.env)
console.log('process.env.BASE_PATH', process.env.BASE_PATH)
console.log("getBasePath() : isProd = " + isProd)
console.log("getBasePath() : basePath = " + basePath)

return basePath
}

module.exports = withCSS(withImages({
generateBuildId: () => {
if (process.env.SOURCE_VERSION) {
return ${process.env.SOURCE_VERSION}
}
else {
return nextBuildId({ dir: __dirname })
}
},
assetPrefix: getBasePath(),
publicRuntimeConfig: {
basePath: getBasePath(),
},
}));`

and I built success on the server, but when access to URL found 404 error all URL
sample pattern URL

• http://subdomain.domain.com/purchases/
• http://subdomain.domain.com/purchases/_next/static/88a138e388b5dab87906f725cf5ecf604ec80eb9/pages/_app.js
• http://subdomain.domain.com/purchases/_next/static/chunks/c8a95c0e1bc00b98bdf7967211209ba8166f0aa5.2a93a51f7edfe8f800ec.js

Could you help me with this issue?